Ninety percent success in palatal implants loaded 1 week after placement: a clinical evaluation by resonance frequency analysis

Modelling the resonant frequency associated with the spatio-temporal evolution of the bone-dental implant interface

Dental implant stability is greatly affected by the mechanical properties of the bone-implant interface (BII), and it is key to long-term successful osseointegration. Implant stability is often evaluated using the Resonant Frequency Analysis (RFA) method, and also by the quality of this interface, namely the bone-implant contact (BIC). True to this day, there is a scarcity of models tying BIC, RFA and a spatially and mechanically evolving BII. In this paper, based on the contact/distance osteogenesis concept, a novel numerical spatio-temporal model of the implant, surrounding bone and evolving interface, was developed to assess the evolution of the interfacial stresses on the one hand and the corresponding resonant frequencies on the other. We postulate that, since the BIC percentage reaches saturation over a very short time, long before densification of the interface, it becomes irrelevant as to load transmission between the implant and the bone due to the existence of an open gap. Gap closure is the factor that provides continuity between the implant and the surrounding bone. The results of the calculated RFA evolution match and provide an explanation for the multiple clinical observations of a sharp initial decline in RFA, followed by a gradual increase and plateau formation. STATEMENT OF SIGNIFICANCE: A novel three-dimensional numerical model of an evolving bone-dental implant interface (BII) is presented. The spatio-temporal evolution of the bone-implant contact (BIC) and the BII, based on contact/distance (CO/DO) osteogenesis, is modeled. A central outcome is that, until BII maturation into a solid continuous bone (no open gap between CO-DO fronts), the bone-implant load transfer is hampered, irrespective of the BIC. The resonant frequencies' evolution of the jawbone-BII-implant is calculated to reproduce the well-established implant stability analysis based on the Resonant Frequency Analysis. The results resemble those reported clinically, and here too, the determinant transition occurs only after interfacial gap closure. Those results should motivate clinicians to re-consider structural continuity of the BII rather than the BIC only.

Correction of Unilateral Posterior Crossbite with U-MARPE

Unilateral posterior crossbite typically presents as a narrow maxillary arch and a broad mandibular arch on the side of the crossbite. Unwanted overexpansion and iatrogenic crossbite may develop as side effects if conventional rapid maxillary expansion is done in such cases. Thus, unilateral expansion of the maxilla with unilateral posterior crossbite can help us avoid these side effects and improve the transverse relationship between the maxillary and mandibular posterior dentition on the affected side only. In this case report, we describe a mini-implant-supported unilateral expansion of the maxillary arch in a patient with a unilateral posterior crossbite.

The clinical significance of implant stability quotient (ISQ) measurements: A literature review

Implant stability quotients (ISQ values) are obtained in dental clinical practice on a non-invasive basis by resonance frequency measurement rapidly after surgical placement of implants. The ISQ-values are used as indicator for mechanical implant stability, and are believed to have predictive power for clinical outcome. It is the aim of this review to provide a synopsis of all factors described in the literature that influence ISQ measurements by performing an exhaustive literature review; moreover, this review aims at elucidating the key factors relevant for a rapid clinical predictive assessment. We searched systematically and exhaustively all major databases for publications relating to ISQ measurement methodology and for ISQ-influencing factor analyses. The reports identified were ordered in experimental (preclinical) studies and in clinical publications. We were able to identify 13 basic factors influencing ISQ-measurements. Among these, local bone quality, playing a key role in such measurements, was subdivided in four specific subfactors; thus a total of 17 individual factors was identified and reported to influence ISQ-measurements. A comprehensive list of these factors is provided in Table-form. A critical analysis points out that only 6 of these factors are of a sound predictive power useful for a rapid clinical assessment; and only two of these factors appear to have a well-documented scientific basis.

Predictive values of resonance frequency analysis as a diagnostic tool in palatal implant loss

OBJECTIVES

To determine the diagnostic value of resonance frequency analysis (RFA) in predicting palatal implant (PI) loss.

MATERIALS AND METHODS

RFA values of 32 patients (study center at Mainz and Dresden) were evaluated in a prospective randomized controlled trial addressing clinical performance of two loading concepts on PI (Orthosystem, Straumann, Basel, Switzerland). Group 1: conventional loading after a 12-week healing period vs group 2: immediate loading within one week after insertion. Stability was assessed by RFA after surgical insertion (T1), one week (T2), and 12 weeks (T3) later.

RESULTS

All 32 PI were clinically stable after surgical insertion; 14 PI were loaded conventionally and 18 immediately. One implant in group 1 was lost 6 weeks after insertion. One drop-out was registered in group 2. One false positive and three false negative implant stability quotients (ISQ) were observed. ISQ values of clinically stable PI in group 1 were 67.2 (SD ± 9.5) at T1, 62.3 (SD ± 11.7) at T2, and 68.2 (SD ± 5.5) at T3. Group 2 showed 67.1 (SD ± 11.7) at T1, 65.4 (SD ± 10.4) at T2, and 72.3 (SD ± 5.6) at T3. Differences between groups were not statistically significant for starting time (P = .88) and change from T1 to T2: 0.08 but were significant from T1 to T3: P = .04; (regression analysis).

CONCLUSIONS

RFA had no sensitivity for prediction of stability. General decrease after primary stability and increase with secondary stability gives support for specificity. Within the limits of the study, only the diagnostic value of RFA identifying stable palatal implants could be confirmed.

Using Resonance Frequency Analysis to Compare Delayed and Immediate Progressive Loading for Implants Placed in the Posterior Maxilla: A Pilot Study

Objective:

Implants placed in the posterior region of the maxilla have a high incidence of implant failure due to poor bone quality, especially when immediate implant loading is needed. Immediate Progressive Loading (IPL) can enhance bone quality and may offer an alternative solution when Immediate Implant loading is needed.

Methods:

Six patients (one male and five females; 34-62 years old) were included in this study. Twelve implants were inserted in the posterior region of the maxilla. Resonance Frequency Analysis (RFA) was performed at the time of implant placement and after 1, 2, 3 and 6 months. ISQ (Implant Stability Quotient) values were compared between the Delayed Loading (DL) group after 2 months and the Progressive Loading (PL) group and between different time points for each group.

Results:

At implant placement, the mean ISQ values for PL and DL implants were 63 and 57, respectively. One month after implant placement, the mean ISQ value for PL implants was 73.

Two months after implant placement, the mean ISQ value for PL implants was 75. Three months after implant placement, the mean ISQ values for PL and DL implants were 76 and 69, respectively. Six months after implant placement, the mean ISQ values for PL and DL implants were 79 and 76, respectively.

Conclusion:

Despite its limitations, this pilot study indicated that compared to DL, PL can enhance bone density and implant stability, resulting in greater early functionality and fewer surgery sessions.

Application of Orthodontic Immediate Force on Dental Implants: Histomorphologic and Histomorphometric Assessment

AIMS

Application of force to implants is helpful, especially in orthodontic-implant therapies. The aim of this study was a histomorphologic and histomorphometric evaluation of peri-implant bone after immediate orthodontic and orthopedic forces comparing them with a control group.

MATERIALS AND METHODS

Eighteen dental titanium implants were inserted in the premolar region of three dogs. Implants were divided into three groups: (1) group with immediate orthodontic force of 300 NC, (2) group with immediate orthopedic force of 600 NC, and (3) control group. Implants were explanted with adequate amount of surrounding bone after 3 months and bone-implant contact (BIC), amount of lamellar bone (LB), amount of woven bone (WB), amount of inflammatory connective tissue, and the rate of the movement were investigated. ANOVA, t-test, paired t-test, and Pearson's test were used to analyze the data using SPSS software version 16 at a significant level of 0.05.

RESULTS

Based on BIC, amount of lamellar and WB and the amount of inflammatory connective tissue, there was no significant difference between the three groups (300 centinewton (CN), 600-CN, and control group) (P > 0.05). In the 300-CN and 600-CN groups, the rate of movement was reported 0.41 and 0.94 with no significant differences (P = 0.38).

CONCLUSION

300-CN and 600-CN immediate static loads do not interfere with osseointegration phenomenon and it does not decrease the amount of BIC and LB. Implants can be moved by preserving osseointegration, and this movement is in direct relation with the amount of applied force.

Implants for orthodontic anchorage: success rates and reasons of failures

INTRODUCTION

The aims of this study were to analyze the success rate of mini-implants and miniscrews and to report the reasons behind them.

MATERIALS AND METHODS

An electronic literature search from PubMed databases and a hand search in implant- and orthodontic-related journals were performed until December 31, 2011. Human clinical studies in English that reported temporary anchorage devices used for orthodontic purpose with at least 6 months follow-up were included. In addition, the minimal number of implants had to be at least 10. Implants placed in maxilla, mandible, and hard palate were included.

RESULTS

The initial search resulted in 847 articles, of which 46 were further evaluated. Finally, 29 studies were qualified and classified into 2 groups: implants placed in maxilla and mandible (group 1) and implants placed in hard palate (group 2). A meta-analysis performed for groups 1 and 2 showed 87.8% and 93.8% survival rate, respectively. In addition, the most common cause for implants failure was surgery-related factors.

CONCLUSION

Mini-implant survival rate is location dependent, with those placed in the palate showing higher success rates. In addition, failures most commonly occur because of surgery-related factors.

Effect of location on primary stability and healing of dental implants

PURPOSE

To study implant primary stability and bone healing using resonance frequency analysis in different anatomical locations 4 months after placement.

MATERIAL AND METHODS

Fifty-six partially edentulous patients restored by dental implants were included. Overall, 214 implants were placed without bone or soft tissue augmentation. All implants were placed with the same drilling protocol and implant insertion torque (35-40 N · cm).

RESULTS

The mean implant stability quotient (ISQ) value at baseline for all the locations was 75.4 mm (95% confidence interval, 74.20-76.59 mm). Higher ISQ values were found in the mandible. A significant difference between ISQ values of each location (P < 0.001) was identified. The mean values obtained showed an increase (3.4%) in all the locations, being greater in the posterior lower and upper maxillae (3.8%), whereas for the anterior maxilla, it was the least (1.5%) 4 months after healing. This increase was statistically significant in the posterior upper and lower maxillae (P < 0.001).

CONCLUSION

Higher implant stability was found in mandible compared with maxilla in both periods, immediately after insertion and 4 months later. Therefore, according to ISQ values, restoring implants immediately after insertion or after a healing period of 4 months represents safe time points.

The Effect of Flapless and Full-thickness Flap Techniques on Implant Stability During the Healing Period

Purpose : When soft tissue flaps are reflected for implant placement, the blood supply from the periosteum to the bone is disrupted. The aim of this study was to compare the effects of the flapless (FL) and full-thickness flap (FT) techniques on implant stability. Methods : Nine patients received 22 implants. The implants were placed using the FL technique on the contralateral side of the jaw; the FT technique was used as the control technique. Resonance frequency analysis (RFA) was performed at the time of implant placement and at 6 and 12 weeks after implant placement. RFA values were compared between the FL and FT groups and between time intervals in the same group. Results : The median (interquartile range [IQR]) RFA values at the time of implant placement were 75.00 (15.00) for the FL technique and 75.00 (9.00) for the FT technique. At 6 weeks, the median (IQR) values were 79 (3.30) for the FL technique and 80 (12.70) for the FT technique. At 12 weeks, the median (IQR) values were 82.3 (3.30) for the FL technique and 82.6 (8.00) for the FT technique. There were no significant differences between the 2 techniques at the time of implant placement, after 6 weeks or after 12 weeks, with p values of 0.994, 0.789, and 0.959, respectively. There were significant differences between the RFA values at the time of implant placement and after 6 weeks for the FL technique (p=0.028) but not for the FT technique (p=0.091). There were also significant differences between the RFA values at 6 weeks and the RFA values at 12 weeks for the FL technique (p=0.007) and for the FT technique (p=0.003). Conclusion : Periosteum preservation during the FL procedure will speed up bone remodeling and result in early secondary implant stability as well as early loading.

Progressive immediate loading of a perforated maxillary sinus dental implant: a case report

The displacement of a dental implant into the maxillary sinus may lead to implant failure due to exposure of the apical third or the tip of the implant beyond the bone, resulting in soft tissue growth. This case report discusses dental implant placement in the upper first molar area with maxillary sinus involvement of approximately 2 mm. A new technique for progressive implant loading was used, involving immediately loaded implants with maxillary sinus perforation and low primary stability. Follow-up was performed with resonance frequency analysis and compared with an implant placed adjacent in the upper second premolar area using a conventional delayed loading protocol. Implants with maxillary sinus involvement showed increasing stability during the healing period. We found that progressive implant loading may be a safe technique for the placement of immediately loaded implants with maxillary sinus involvement.

Resonance Frequency Analysis of 208 Straumann Dental Implants During the Healing Period

The most important prerequisite for the success of an osseointegrated dental implant is achievement and maintenance of implant stability. The aim of the study was to measure the 208 Straumann dental implant stability quotient (ISQ) values during the osseointegration period and determine the factors that affect implant stability. A total of 164 of the implants inserted were standard surface, and 44 of them were SLActive surface. To determine implant stability as ISQ values, measurements were performed at the stage of implant placement and healing periods by the Osstell mentor. The ISQ value ranges showed a significant increase during the healing period. Except for the initial measurement, the posterior maxilla had the lowest ISQ values, and there was no significant difference among anterior mandible, posterior mandible, and anterior maxilla (P &lt; .05). Implant length did not have a significant influence on ISQ value (P &gt; .05). The second measurement was significantly higher in men compared with women (P &lt; .05). The second measurement was significantly higher than the others at 4.8 mm, and for the final measurement, there were no significant differences between 4.8 and 4.1 mm, which were higher than 3.3 mm (P &lt; .05). When comparing sandblasted, large-grit, acid-etched (SLA) and SLActive surface implants, there were no significant differences for insertion measurements, but for second measurements, SLActive was significantly higher (P = 0), and for the final measurement, there was no significant difference. It appears that repeated ISQ measurements of a specific implant have some diagnostic benefit, and the factors that affect implant stability during the healing period are presented.

Success rate of paramedian palatal implants in adolescent and adult orthodontic patients: a retrospective cohort study

The purpose of this study was to examine the success rate of paramedian palatal Orthosystem first- and second-generation implants used for anchorage in orthodontic treatment in patients treated by one experienced orthodontist. The records of 143 patients (90 female, 53 male, median age: 15.7 years, range: 10.2-50.9) receiving 145 palatal implants of the first or second generation (Orthosystem, Straumann AG, Basel, Switzerland) were examined. All the palatal implants were placed in a paramedian palatal location by three experienced surgeons. Stable implants were orthodontically loaded after a healing period of 3 months. Out of the 145 inserted paramedian palatal implants only seven implants (4.8%) were not considered stable after insertion. All the successfully osseointegrated implants remained stable during orthodontic treatment. Paramedian palatal implants are highly reliable and effective devices to obtain skeletal anchorage for orthodontic treatment. This study has shown that the paramedian location is a good alternative to the median location.

Evaluation of the palatal bone for placement of orthodontic mini-implants in Japanese adults

Mini-implants are increasingly being used for orthodontic anchorage in the palate. The anatomical structure of the jaw must be properly evaluated prior to use; however, there are a few research reports providing basic data regarding the palate. Bone thickness was measured and bone morphology evaluated in the palates of Japanese people. The palates of five Japanese adult cadavers and 15 skulls were examined. The samples were imaged and measured using the micro-CT system. In the mid-palatine suture region, the cortical bone had a complex mesh-like structure and was thicker than surrounding areas. Cortical bone thickness varied depending on the site. The mid-palatine suture region is an ideal site for mini-implant insertion; however, because bone and cortical bone thickness markedly decrease in the lateral region, careful attention should be paid when inserting mini-implants in the mid-palatine suture.

Evaluation of palatal bone density in adults and adolescents for application of skeletal anchorage devices

OBJECTIVES

To measure the cortical and cancellous bone densities of the palatal area in adolescents and adults and to compare bone quality among placement sites of temporary anchorage devices.

MATERIALS AND METHODS

One hundred twenty cone beam computerized tomography scans were obtained from 60 adolescents (mean age, 12.2 ± 1.9 years) and 60 adults (24.7 ± 4.9 years). The measurements of palatal bone density were made in Hounsfield units (HU) at 72 sites at the intersections of eight mediolateral and nine anterioposterior reference lines using InVivoDental software. Repeated-measures analysis of variance was used to analyze intragroup and intergroup differences.

RESULTS

The cortical and cancellous bone densities in the adults (816 and 154 HU, respectively) were significantly higher than those in the adolescents (606 and 135 HU; P < .001 and P  =  .032, respectively). However, the anterior portion of the cortical bone in adolescents had similar density values to the posterior portion of the cortical bone in adults. Gender comparison revealed that females had greater cortical bone densities (769 HU) than their male counterparts did (654 HU; P < .001).

CONCLUSIONS

Palatal bone densities were significantly higher in adults than in adolescents, and the anterior palatal areas of adolescents were of similar values to those at the posterior palate of adults.

Clinical study of temporary anchorage devices for orthodontic treatment--stability of micro/mini-screws and mini-plates: experience with 455 cases

The aim of this retrospective study was to determine factors that might cause complications in use of temporary anchorage devices (TADs) for orthodontic anchorage. We investigated 904 TADs in 455 patients. Clinical diagnoses requiring orthodontic treatment were malocclusion, jaw deformity, various syndromes, cleft lip and palate and impacted teeth. All patients underwent surgery at Tokyo Dental College Chiba Hospital between November 2000 and June 2009. Three kinds of titanium screw of different diameter and length were used: self-drilling mini-screws (Dual Top Autoscrew® and OSAS®), pre-drilling micro-screws (K1 system®) and palatal screws (PIAS®). Mini-plates fixed with 2 or 3 screws (SAS system®) were also used for skeletal anchorage. Patients were aged between 8 and 68 years (25.7±9.8 years). A total of 460 screw-type and 444 plate-type TADs were used. These comprised the following: mini-plates, 444; self-drilling mini-screws, 225; pre-drilling micro-screws, 83; and palatal screws, 152. Each type of implant had a high success rate of over about 90%. Failure rates were as follows: micro-screws, 7%; mini-screws, 6%; palatal implants, 11%; and mini-plates, 6%. Inflammation rate occurring in soft tissue surrounding TADs was follows: plate-type, 7.6%; mini-screws, 1.3%; micro-screws, 0%; and palatal implants, 2.5%. Inflammation frequencies depended on degree of mucosal penetration. Granulation rate in soft tissue surrounding TADs occurred as follows: micro-screws, 5.7%; self-drilling mini-screws, 0%; palatal screws, 0.6%; plate-type, 0.9%. Both plate- and screwtype orthodontic implants showed excellent clinical performance.

Factors influencing resonance frequency analysis assessed by Osstell mentor during implant tissue integration: II. Implant surface modifications and implant diameter

OBJECTIVES

To monitor the development of the stability of Straumann tissue-level implants during the early phases of healing by resonance frequency analysis (RFA) and to determine the influence of implant surface modification and diameter.

MATERIAL AND METHODS

A total of twenty-five 10 mm length implants including 12 SLA RN v4.1 mm implants, eight SLActive RN v4.1 mm implants and five SLA WN v4.8 mm implants were placed. Implant stability quotient (ISQ) values were determined with Osstell mentor at baseline, 4 days, 1, 2, 3, 4, 6, 8 and 12 weeks post-surgery. ISQ values were compared between implant types using unpaired t-tests and longitudinally within implant types using paired t-tests.

RESULTS

During healing, ISQ decreased by 3-4 values after installation and reached the lowest values at 3 weeks. Following this, the ISQ values increased steadily for all implants and up to 12 weeks. No significant differences were noted over time. The longitudinal changes in the ISQ values showed the same patterns for SLA implants, SLActive implants and WB implants. At placement, the mean ISQ values were 72.6, 75.7 and 74.4, respectively. The mean lowest ISQ values, recorded at 3 weeks, were 69.9, 71.4 and 69.8, respectively. At 12 weeks, the mean ISQ values were 76.5, 78.8 and 77.8, respectively. The mean ISQ values at all observation periods did not differ significantly among the various types. Single ISQ values ranged from 55 to 84 during the entire healing period. Pocket probing depths of the implants ranged from 1 to 3 mm and bleeding on probing from 0 to 2 sites/implant post-surgically.

CONCLUSIONS

All ISQ values indicated the stability of Straumann implants over a 12-week healing period. All implants showed a slight decrease after installation, with the lowest ISQ values being reached at 3 weeks. ISQ values were restored 8 weeks post-surgically. It is recommended to monitor implant stability by RFA at 3 and 8 weeks post-surgically. However, neither implant surface modifications (SLActive) nor implant diameter were revealed by RFA.

Bone response to early orthodontic loading of endosseous implants

This study evaluated the clinical, radiographic, and histologic responses of tissues surrounding implants loaded with a heavy force of 500g for 20 weeks after a 1-week healing period. Unilateral mandibular and maxillary alveolar ridges in the premolar areas of a male dog and the bilateral mandibular alveolar ridges of a female dog were chosen for implant placement. The control implants (1 in the maxilla, 3 in the mandible) were placed in these quadrants after a 12-week healing period following extraction. The test implants (1 in the maxilla, 3 in the mandible) were implanted in the same quadrants after a 4-month osseointegration period of the control implants. Abutments were attached to the control and test implants after a 1-week healing period for the test implants. Superelastic nickel-titanium coil springs, producing a force of 500g (≈5 N), were activated between control and test implants for 20 weeks. Light microscopic assessment revealed that all implants were well integrated with the bone. Histologic analysis showed no definitive differences between test and control implants in the corticalization of bone trabeculae. The mean bone-implant contact values of the control implants for compression and tension sides were 55.99% and 64.04%, respectively. In the test implants, the bone-implant contact value was 57.27% for the compression side and 62.96% for the tension side. Potential clinical applications of these radiologic and histologic results include the possibility of minimizing the healing duration, even for high orthodontic forces, and the possibility of postorthodontic use of these implants as abutments for supporting prosthetic reconstruction.

Survival and failure rates of orthodontic temporary anchorage devices: a systematic review

AIM

The purpose of this study was to systematically review the literature on the survival rates of palatal implants, Onplants((R)), miniplates and mini screws.

MATERIAL AND METHODS

An electronic MEDLINE search supplemented by manual searching was conducted to identify randomized clinical trials, prospective and retrospective cohort studies on palatal implants, Onplants((R)), miniplates and miniscrews with a mean follow-up time of at least 12 weeks and of at least 10 units per modality having been examined clinically at a follow-up visit. Assessment of studies and data abstraction was performed independently by two reviewers. Reported failures of used devices were analyzed using random-effects Poisson regression models to obtain summary estimates and 95% confidence intervals (CI) of failure and survival proportions.

RESULTS

The search up to January 2009 provided 390 titles and 71 abstracts with full-text analysis of 34 articles, yielding 27 studies that met the inclusion criteria. In meta-analysis, the failure rate for Onplants((R)) was 17.2% (95% CI: 5.9-35.8%), 10.5% for palatal implants (95% CI: 6.1-18.1%), 16.4% for miniscrews (95% CI: 13.4-20.1%) and 7.3% for miniplates (95% CI: 5.4-9.9%). Miniplates and palatal implants, representing torque-resisting temporary anchorage devices (TADs), when grouped together, showed a 1.92-fold (95% CI: 1.06-2.78) lower clinical failure rate than miniscrews.

CONCLUSION

Based on the available evidence in the literature, palatal implants and miniplates showed comparable survival rates of >or=90% over a period of at least 12 weeks, and yielded superior survival than miniscrews. Palatal implants and miniplates for temporary anchorage provide reliable absolute orthodontic anchorage. If the intended orthodontic treatment would require multiple miniscrew placement to provide adequate anchorage, the reliability of such systems is questionable. For patients who are undergoing extensive orthodontic treatment, force vectors may need to be varied or the roots of the teeth to be moved may need to slide past the anchors. In this context, palatal implants or miniplates should be the TADs of choice.

Bone quality in the midpalate for temporary anchorage devices

OBJECTIVE

The aim of the present study was to quantitatively assess the bone quality of the palatal bone from an implantologic standpoint.

MATERIAL AND METHODS

The material consisted of palatal tissue blocks of autopsy material from 22 subjects (19 male, three female), between 18 and 63 years of age. The specimens comprised the anterior part of median palate (APMP) from about 7 mm behind the incisive foramen (first premolar regions), the middle part of median palate (MPMP, second premolar region), and the posterior part of the median palate (PPMP, first molar region). They were prepared in the transversal plane using ground-thin-section technology. The midpalatal areas of the different parts of the palate [regions of interest (ROI) for temporary anchorage device (TAD) placement] 3 mm bilaterally to the midline were assessed with respect to hard tissue fraction to total bone volume (HTF/TBV), bone marrow fraction to total bone volume (BMF/TBV), and sutural tissue fraction to total bone volume (STF/TBV). Furthermore, age-specific evaluation was performed: younger age group (18-25 years, n=10) and older age group (26-63 years, n=12).

RESULTS

Histomorphometric measurement showed the following results for the APMP: mean HTF/TBV, 68.57%; mean BMF/TBV, 21.38%; and mean STF/TBV, 9.96%. There were no statistically significant differences between the various tissue fractions of the APMP, MPMP, and PPMP. The younger age group showed a mean HTF/TBV of 68.88%, a mean BMF/TBV of 21.5%, and a mean STF/TBV of 9.53%. No statistically significant differences with the older age group were found.

CONCLUSION

These results suggest that the HTF in the APMP, MPMP, and PPMP in younger as well as older adults is relatively high. Thus, good primary stability of TADs should be achieved in all parts of the adult median palate independent of age.

Success rate of miniscrews relative to their position to adjacent roots

The purpose of this study was to evaluate, histologically, root contact, proximity to a root, and proximity to marginal bone level as possible risk factors for the failure of mini-screws when inserted between neighbouring teeth. Twenty mini-screws were inserted into the mandible of five beagle dogs. Each dog received two bracket screw bone anchors in each lower quadrant, between the roots of the second and third, and third and fourth premolars. Every six weeks, apical radiographs were taken and vital stains were administered. Twenty-five weeks after insertion of the screws, the dogs were sacrificed and specimens prepared for histological evaluation. The distance between the screw and the roots and between the screw and the marginal ridge level (MRL) were measured on the histological slides. The presence or absence of root contact was evaluated histologically on serial sections. The number of screws was too small to allow for sound statistical analysis of the factors under investigation. During the evaluation period, 11 screws were lost. Six screws were in contact with a tooth root and five of these were lost. In five sites, the distance between the screw and the tooth was less than 1.0 mm, but only one of these screws was lost. The distance between the screw and the marginal bone level was less than 1.0 mm for nine screws and seven of these were lost. The results of this limited study suggest that root contact and marginal position might be major risk factors for screw failure.

Success rate of palatal orthodontic implants: a prospective longitudinal study

AIM

The purpose of this prospective cohort study was to assess the survival and success rates of palatal implants.

MATERIAL AND METHODS

Seventy patients (56 female, 14 male; age 25-6 +/- 10-8 years) receiving Orthosystem (Straumann AG, Basel, Switzerland) palatal implants from March 1999 to November 2006 were included. The indication was established according to the required anchorage for orthodontic therapy. All implants were placed in a mid-sagittal, median or paramedian palatal location by the same surgeon. They were orthodontically loaded after a healing period of 8-16 weeks (Mean: 12.8 weeks).

RESULTS AND DISCUSSION

Of the initially 70 consecutively admitted patients, two implants in two patients were not primary stable after installation and had to be removed. Of the 70 initially installed palatal implants, 67 implants or 95.7% osseointegrated successfully and were loaded actively and/or passively for approximately 19 months. Only one implant of the 67 osseointegrated implants lost its stability under orthodontic loading. By the time of re-evaluation, 20 palatal implants were still used for orthodontic therapy, while 46 implants had been removed after completed orthodontic therapy. By only analyzing those, the success rate of the initially installed implants was 92%.

CONCLUSIONS

Orthodontic palatal implants with a rough surface are predictable and highly reliable devices for a multitude of maxillary orthodontic treatment options. The survival and success rates for palatal orthodontic implants are comparable to dental implants installed for dental prostheses.

Early loading of plalatal implants (ortho-type II) a prospective multicenter randomized controlled clinical trial

BACKGROUND

In orthodontic treatment, anchorage control is a fundamental aspect. Usually conventional mechanism for orthodontic anchorage control can be either extraoral or intraoral that is headgear or intermaxillary elastics. Their use are combined with various side effects such as tipping of occlusal plane or undesirable movements of teeth. Especially in cases, where key-teeth are missing, conventional anchorage defined as tooth-borne anchorage will meet limitations. Therefore, the use of endosseous implants for anchorage purposes are increasingly used to achieve positional stability and maximum anchorage.

METHODS/DESIGN

The intended study is designed as a prospective, multicenter randomized controlled trial (RCT), comparing and contrasting the effect of early loading of palatal implant therapy versus implant loading after 12 weeks post implantation using the new ortho-implant type II anchor system device (Orthosystem Straumann, Basel, Switzerland). 124 participants, mainly adult males or females, whose diagnoses require temporary stationary implant-based anchorage treatment will be randomized 1:1 to one of two treatment groups: group 1 will receive a loading of implant standard therapy after a healing period of 12 week (gold standard), whereas group 2 will receive an early loading of orthodontic implants within 1 week after implant insertion. Participants will be at least followed for 12 months after implant placement. The primary endpoint is to investigate the behavior of early loaded palatal implants in order to find out if shorter healing periods might be justified to accelerate active orthodontic treatment. Secondary outcomes will focus e.g. on achievement of orthodontic treatment goals and quantity of direct implant-bone interface of removed bone specimens. As tertiary objective, a histologic and microtomography evaluation of all retrieved implants will be performed to obtain data on the performance of the SLA surface in human bone evaluation of all retrieved implants. Additionally, resonance frequency analysis (RFA, Osstell mentor) will be used at different times for clinically monitoring the implant stability and for histological comparison in order to measure the reliability of the resonance frequency measuring device.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN97142521.

Natural Frequency Analysis of Osseointegration for Trans-femoral Implant

Osseointegration trans-femoral implants are a new orthopaedic anchoring method to attach prosthetic limbs. The clinical success of this promising technique depends on the effectiveness of osseointegration achieved after implantation. The aim of this study is to use the resonant characteristics of the implant system to determine the changes in stability as a reflection of boundary condition of the implant. With a small mechanical excitation, Vibration responses of the trans-femoral implant to a small mechanical excitation were measured using an accelerometer and the vibration signal was analyzed using Fast Fourier Transform (FFT) software to obtain the fundamental natural frequency (NF) of the implant system. In-vitro study was conducted using different silicone rubbers to simulate the interface condition. The result showed that a high NF corresponded to a high elastic modulus of the interface material between the implant and bone. A preliminary in-vivo study with one osseointegration trans-femoral implant patient showed that there was a decrease of NF after initial weight bearing rehabilitation. After continued weight bearing, the NF gradually returned to the pre-loading level at around day 24 and the general trend of the NF reached a stable state 38 days after the first weight bearing exercise.